Colicin E6

Colicin E6 is a type of Colicin, a bacteriocin made by E. coli which acts against other nearby E. coli to kill them with its 16s rRNase activity; it digests the 16s ribosomal subunit, ultimately leading to the death of the cell.

Synthesis and release
The ColE6 operon is encoded on a plasmid in the E. coli cell, and includes the Colicin Immunity Protein, ImmE6. Once the colicin has been produced, it binds to its immunity protein; this protects the colicinogenic cell from the cytotoxic activity of the colicin.

Mechanism of uptake
The receptor binding domain of ColE6 binds to BtuB, which triggers the dissociation of the immunity protein, so the cytotoxic domain can act when the colicin enters the cell. Once bound to BtuB, the complex recruits OmpF, and the TolQRAB complex, to transport the colicin across the membrane, using a mechanism not yet identified.

Killing Activities
ColE6 kills its target cell with its 16s rRNase activity, found on its C terminus. This enzymatically degrades the 16s rRNA subunit, preventing the cell from synthesising any proteins, and ultimately killing the cell.